This invention relates generally to a method and apparatus for recording and reproducing an information signal and, more particularly, is directed to a method and apparatus for recording and reproducing a color television signal comprising a video signal and an audio signal on a magnetic tape with a plurality of rotary magnetic heads.
Information signal recording and reproducing apparatus for recording and reproducing a video signal on a magnetic tape by means of a rotary magnetic head assembly are well known in the art. For example, in a helical scan video tape recorder (VTR), at least one rotary magnetic head is rotated at a predetermined angle with respect to the longitudinal or tape running direction of a magnetic tape as the latter is advanced so as to form successive video tracks extending obliquely on the magnetic tape. With the helical scan video tape recorder, it is possible to achieve high density recording of the video signal by advancing the magnetic tape at a slow running speed and, at the same time, providing a high relative speed between the magnetic head assembly and magnetic tape. However, with known helical scan video tape recorders in which an audio signal is recorded and reproduced on an audio track extending in the longitudinal or tape running direction of the magnetic tape by a stationary magnetic head, there results a deterioration of the signal-to-noise (S/N) ratio and an increase in the wow and flutter when the speed of advancement of the magnetic tape is reduced. This, of course, results in a deterioration in the quality of the reproduced audio signal, causing the audio signal to have unsatisfactory quality when reproduced.
In order to overcome the aforementioned problem in the recording and reproducing of an audio signal by a stationary magnetic head, it has been proposed to effect the recording and reproducing of the audio signal by means of a rotary magnetic head. With this proposal, an overscan section is provided for each oblique track, for example, by increasing the tape winding angle about the guide drum assembly of the helical scan video tape recorder. In this manner, each record track obliquely formed on the magnetic tape by the rotary magnetic head assembly includes a video track section and an audio track section, the latter of which corresponds to the aforementioned overscan section. The audio signal that is recorded and reproduced with respect to the audio track section of each track is processed as high density data obtained by processing the signal with a time axis or base compression and a time axis or base expansion.
In one known apparatus, two rotary magnetic heads are provided and are spaced apart by 180.degree.. Thus, each head scans alternate ones of the successive tracks extending obliquely on the magnetic tape. It has been proposed to digitize and compress the audio signal and recorded the same in the overscan section at the beginning of each track with such known apparatus. Such arrangement provides the desirable feature of recording the video signal and the high quality digitized audio signal in separate sections of each track. In some cases, it may also be desirable to record only the digitized audio signal in the entire portion of each track, that is, in the video track section and audio track section, without reproducing any video signal therein. With this latter arrangement, since the audio signal is recorded as a digitized audio signal, high quality audio reproduction can be achieved. However, because the audio signal is recorded in digital form, error correction codes, run-in or preamble signals and the like are added to the digitized audio signal. Further, because the digitized audio signal is compressed, the digitized audio signal is an intermittent signal, that is, with time gaps between compressed portions of the digitized audio signal. As a result, timing of the audio signal to be recorded in the entire portion of each record track makes it difficult to utilize the same circuitry as that used for processing a digitized audio signal which is recorded in only the overscan section of each track and combined with a video signal recorded in the main section of each track, thereby requiring the use of separate audio processing circuitry. This duplication of circuitry, of course, becomes wasteful and relatively expensive. It is to be further appreciated that, if an audio signal is successively recorded in the entire portion of each track, it becomes relatively time consuming and bothersome to search for a particular audio selection.